`azurerm_cdn_frontdoor_profile` - add support for the `identity` property

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The purpose for this PR are as follows:

[X] I have followed the guidelines in our Contributing Documentation.
[X] I have checked to ensure there aren't other open Pull Requests for the same update/change.
[X] I have checked if my changes close any open issues. If so please include appropriate closing keywords below.
[X] I have updated/added Documentation as required written in a helpful and kind way to assist users that may be unfamiliar with the resource / data source.
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Below please provide what should go into the changelog (if anything) conforming to the Changelog Format documented here.

ENHANCEMENTS:

cdn - upgrade api version to 2024-02-01 for the AFD Profile resource [GH-00000]
azurerm_cdn_frontdoor_profile - add support for the identity property [GH-00000]

This is a (please select all that apply):

Fixes #20289

[!NOTE] If this PR changes meaningfully during the course of review please update the title and description as required.